The subject matter disclosed herein relates to computed tomography systems and, in particular, to x-ray sources for such systems.
Future Computed Tomography (CT) medical imaging systems will be designed to perform volumetric, “organ-in-a-rotation” scanning. This requirement imposes significant increases in temporal resolution and axial coverage. In turn, this necessitates that the component x-ray tube produce x-rays that cover an increased axial extent with uniform intensity and that the tube be able to withstand mechanical stresses incurred as a result of faster gantry rotation speeds in the CT medical imaging (hereinafter scanning) systems.
CT imaging involves computer-aided reconstruction of an image internal to an object or a human patient, where the reconstructed image is generated from a plurality of views taken at a succession of different scan angles as the gantry rotates around the object or the patient. In an ideal scanning procedure, the plurality of views would lie in a single plane. However, as multi-slice scanning systems have become the industry norm, and the detector used in scanning systems is, accordingly, a component disposed in a distributed configuration along the axis of rotation, image reconstruction requires the processing of non-planar views. Reconstructed images are normally acceptable for an axial coverage of up to about 40 mm (i.e., the extent of the imaged area). However, for larger axial coverage, unacceptable levels of image artifacts are created when a single x-ray source is used in the scanning system. This problem is addressed in the present state of the art by providing multiple x-ray source locations along the rotation axis to increase axial coverage.
This is an emerging paradigm in CT systems for multi-spot systems. For example, U.S. Pat. No. 6,125,167 “Rotating anode x-ray tube with multiple simultaneously emitting focal spots” discloses an x-ray tube comprising a plurality of anode elements. A corresponding plurality of cathode assemblies function to generate a series of parallel x-ray beams.
The inventors herein have recognized a need for an x-ray source producing an x-ray beam that covers a target axial extent with substantially uniform intensity.